In order to keep the gases entering into a trace detecting device, such as an ion mobility spectrometer clean, the gases entering into the ion mobility spectrometer is generally purified by using a gas purification device. The moisture and impurity in the gas are removed mainly by the desiccant in the gas purification device during a gas purifying process, and the desiccant is renewable by a series of high temperature baking and cooling processes so as to be recycled.
In the existing ion mobility spectrometers, a single gas purification device is used in some ion mobility spectrometers, in which the gas is dried by the desiccant disposed in the gas purification device, which requires replaced periodically in a short time. During the replacement, the ion mobility spectrometer cannot be used nor continuous work, and thus the maintenance cost is high. Moreover, two gas purification devices are used in some ion mobility spectrometers, in which the gas is dried in turn by the desiccants disposed in the gas purification devices, that is, when replacing one gas purification device, the other one is used, so as to achieve continuous works. However, in this case, the gas purification device is required to be replaced periodically and the desiccant is not recyclable. Therefore, the gas purification devices in the existing ion mobility spectrometers have disadvantages of manual replacement, low efficiency and high cost.